Animal Nutrition Exam III

Roles of Digestive Tract 

absorbing nutrients, rid the body of waste, break down food, and some immune responses like producing enzymes 

roles of saliva

moisten food, produces salivary amylase (starch digestion, ruminants do not have amylase), buffers rumen pH 

3 main salivary glands

parotid, sublingual, mandibular (PSM-Parker can Sub for spanish(lingual) with Mandi)

Deglutition 

fancy word for swallowing 

Peristalsis

movement of food down the esophagus (like a snake)

Regions of the stomach

cardiac: produces mucus for lubrication and protection, fundic: produces enzymes and hydrochloric acid, pyloric: secretes hormones and mucus

Parietal cells

produce HCl

chief cells

secrete pepsinogen

zymogen

non-activated hormone that must be activated by an enzyme

small intestine

major site of digestion and absorption

roles of small intestine

Duodenum, Jejunum, Ileum

Duodenum

addition of digestive juices, pancreatic enzymes, bicarb, bile salts, enterocyte secretions

Jejunum

where most absorption occurs

Ileum

a major site of immune function, the transition from the small intestine to the large intestine, little absorption

villi

increase the surface area

Bile

stored in the gallbladder is secreted to aid in fat emulsification

areas of large intestine

cecum, colon, rectum (CeCoRe)

cecum

fermentation, large in hindgut fermenters

colon

some absorption of short-fatty acids

rectum

excretion of feces 

what happens in large intestine?

microbial fermentation, synthesis of some water-soluble vitamins

enzymes

protease, lipase, amylase

protease

breaks down protein

lipase

breaks down fats

amylase

break down starch

Glucose Transportation

SGLT1, GLUT5, GLUT2

SGLT1

Sodium-Glucose Linked Transporter 1: brings glucose into the enterocyte from the intestinal Lumen 

GLUT5

brings fructose into the enterocyte from the Lumen

GLUT2

Brings Glucose OUT of the enterocyte and into circulation

GI tract hormones 

gastrin, ghrelin 

gastrin

stimulates HCl and pepsin productions

ghrelin

increases hunger signaling

Incretins

secreted by the small intestine in the presence of food. They “prime” the pancreas for insulin secretion.

examples of Incretins

GLP-1, GLP-2

Gut Peptide Hormones

Cholecystokinin (CCK), peptide YY (PYY). Both decrease feed intake

cholecystokinin (CCK)

release of digestive enzymes and bile into the small intestine, decreases feed intake

Peptide YY (PYY)

increases retention in the intestine and water/electrolyte absorption, decreases feed intake 

rumination

regurgitation and rechewing of cud (a bolus of food), and breaks down the food even more, increasing surface area for microbial digestion

cows digestive tract

rumen, reticulum, omasum, abomasum, papili

rumen

site of microbial fermentation and VFA absorption 

reticulum

mixing and regurgitating feed

omasum

water absorption

Abomasum

“True stomach” secretes HCl and digestive enzymes to break down feed

papili

used to increase surface area

Volatile Fatty Acids (VFA)

produced by rumen

examples of VFAs

Acetate, Propionate, Butyrate

Acetate

Used as the primary source of acetyl-CoA for lipid synthesis

propionate

key substrate for glucose production 

butyrate

oxidized in tissue for energy production

microbes in prokaryotes

bacteria, archaea

microbes in eukaryotes

Protozoa, fungi

Why can’t horses throw up?

esophagus only allows for one way peristaltic movement.(will drown)

Effect of Horses not having a gallbladder 

will have less bile secretion, has a hard time breaking down fats 

horses cecum

enlarged to aid in fiber digestion

Hindgut Acidosis

1. Significant increase in starch

2. increase in lactic acid in the hindgut

3. pH drops

4. decreasing in fiber-digesting bacteria and an increase in lactate-producing bacteria

5. death of bacteria

6. release endotoxins

7. causes inflammation

8. inflammation—> changes in laminae 

Avians

Crop, Proventriculus, Gizzard, 2 Ceca, excretes nitrogen via uric acid mixed into feces 

crop

regulates the flow of food to the lower GI tract. Allows breakdown by salivary amylase

proventriculus

production of HCl and pepsin

gizzard

mixing and grinding feed, CONTAINS GRIT

2 ceca

reabsorbs water

What is Energy measured in?

Joules and calorie & Calorie

Joules

standard international unit of energy. 1 cal=4.186 J

calorie (cal)

heat required to raise the temperature of 1 gallon of water 1 degree higher

Calorie

=1kcal=1000 calorie

Types of Energy

Kinetic, Potential, sound, light

Kinetic energy 

thermal, mechanical, electrical, magnetic 

potential energy

chemical, elastic, nuclear, gravitational

Energy Consumers

autotroph, heterotrophs, each time energy is transferred from one entity to another, some energy is lost as heat 

Autotroph 

can use atmospheric CO2

Phototrophs, and lithotrophs

phototrophs

uses light energy (photosynthetic bacteria and plants)

heterotrophs

cannot use atmospheric CO2

must obtain carbon from their environment from organic molecules (all animals fall in this category) 

Positive energy balance

the animal will gain weight 

Neutral energy balance

the animal will maintain its weight

negative energy balance

the animal will lose weight

gross energy

the total chemical energy in feed

digestible energy

The amount of energy in the feed - the amount of energy lost in the feces

metabolizable energy

the amount of energy in the feed - the energy lost in heat

net energy

The amount of energy in the feed - the energy lost in the feces, urine, and heat production through digestive and metabolic processes

energy partitioning scheme

GEFEDEGUMHINE

%TDN: total digestible nutrients 

digestible protein + digestible fiber + digestible nitrogen free extract + digestible (Fat x 2.25) 

DE

GE-fecal

ME

DE - urine - gas

NE

ME - heat

Energetic Efficiency

(NE/GE) x 100

NE(L)

net energy for lactation. milk synthesis

NE(G)

net energy for growth. Tissue fat accretion

NE(M)

Net energy for Maintenance.

Basal metabolism, posture, movement, thermoregulation, and maintenance of homeostasis 

energetic efficiency

metabolizable energy (ME)/Net energy (NE) x 100

Respiratory Quotient

can estimate an animal’s energy balance

• it reflects the ratio of carbon dioxide produced to oxygen consumed during respiration (varies on the type of nutrient being used for E) 

ATP

major form of cellular energy, 2 phosphoanhydride bonds (high E)

Tricarboxylic acid (TCA) cycle

citric acid = krebs cycle, takes place in mitochondrial matrix

Oxidative Phosphorylation

links oxidation of high E molecules (NADH, FADH2) to the addition of a phosphate group to ADP to form ATP

Aerobic Respiration of Glucose

Gluconeogenesis

synthesis of glucose

substrates of Gluconeogenesis

glycerol, amino acids, lactate, propionate

beta-oxidation

conversion of fats to energy

Homeostasis

maintenance of physiological equilibrium

Homeohesis

orchestrated or coordinated in tissue metabolism necessary to support the priorites of a physiological state 

homeohesis vs. homeostasis

changes a threshold based on changes in need vs. tries to maintain status quo